1. Field of the Invention
This invention pertains generally to aircraft systems and, more particularly, to aircraft systems including arc fault protection. The invention also pertains to a method of arc fault protection for an aircraft system.
2. Background Information
It is known to employ thermal fuses between an avionics power source and the seat electronics boxes of an aircraft entertainment system, with one thermal fuse per corresponding seat electronics box. While this thermal fuse arrangement can deal with overcurrent conditions, it cannot respond to arc faults (e.g., line-to-line; line-to-frame).
During sporadic arc fault conditions, the overload capability of a circuit breaker will not function since the root-mean-squared (RMS) value of the fault current is too small to actuate the automatic trip circuit. The addition of electronic arc fault sensing to a circuit breaker can add one of the elements required for sputtering arc fault protection—ideally, the output of an electronic arc fault sensing circuit directly trips and, thus, opens the circuit breaker. See, for example, U.S. Pat. Nos. 6,710,688; 6,542,056; 6,522,509; 6,522,228; 5,691,869; and 5,224,006.
Aircraft circuit breakers have employed various mechanisms to indicate arc fault events. For example, U.S. Pat. No. 6,542,056 discloses a movable and illuminable arc fault indicator having a ring portion and two leg portions internal to a housing. When energized by an arc fault current assembly in response to an arc fault trip condition, an arc fault actuator moves one of the leg portions internal to the housing, which, in turn, moves the ring portion external to the housing. The arc fault current assembly includes a light emitting diode (LED) for illuminating the ring portion through the other one of the leg portions when the arc fault current assembly is properly powered and in the absence of an arc fault trip condition.
Application Ser. No. 11/129,909 discloses an arc fault circuit breaker including a first LED for a first status (e.g., an arc fault trip status) and a second LED for a second status (e.g., a health status). The first LED illuminates a transparent operating handle. The second LED protrudes through the circuit breaker housing and through a device key-hole in a panel.
There is room for improvement in aircraft systems.
There is also room for improvement in methods of arc fault protection for an aircraft system.